Vinyl chloride polymer foams by treatment with a bis (azidoformate) modifying agent and a blowing agent



the azidoformate thioethers such as 2,2-thiodiethyl-bis- 6 United StatesPatent ce Patented Oct. 12, 1965 (azidoformate),4,4'-thiodibutyl-bis(azidoformate; etc. 3,211,677 It will, of course, beobvious to those skilled in the art that still other azidoformatescontaining functional ING AGENT AND A BLOWING AGENT Iage inert tomodification reactions, such as George B. Feild, New Castle, and John R.Lewis, Wilmington, DeL, assignors to Hercules Powder Company, 0

gilrligington, a coirporation of Delaware 0 y 2??? 296426 eto., groups,are included in the above definition. The 10 azidoformates used in thisinvention can be prepared in This invention relates to a process forpreparing poly- Vaflous Ways, as r eXamPIe Y reacting the respective merfoams. More particularly, the invention relates to chlhl'oformate Withan excess, from about mole a process for preparing modified foams ofvinyl chloride t0 ahellt 0 m s per equivalent of chl m of h polymers andto the modified foams so prepared. alkah azlde- It is known to use vinylchloride polymers in the y of the weh'khowh'chemlcal blowing agents canhe preparation f expanded materials he foams, by used in the preparationof the foams in accordance with corporating in the polymer a chemicalblowing agent thigmventionas, for x mp 1110 bis(formamide), a whichunder the i fl of heat evolves gas whereby aminobenzene,N,N-d1n1trosopentamethylene tetramine, cells are formed and a lowdensity product is produced. N Y h P h, 1P P" Y' However, the prior artprocesses suffer several disadfi e e shlfohyl SeImCaThaDde), 3Z0 hls hvantages. For example, pressures of about 10,000 p.s.i. F PP'fOXYb1S(behZehe shlfohyl hydrazlde): are usually required during thedecomposition of the P:P" l? Y l hydr'tlzide), hehzehe'shlfohyl blowingagent, then the product must be cooled (still hydralldeambenzehehlstshlfohyl hydrazide) Any under pressure) and finally reheatedwithout the appli- P the weh'khowh Solvent hlowlhg agents can he dcation f pressure to ff t expansion The foams 5 in this invention as,for example, monochlorotrifluorome- Sulting from such processes remainthermoplastic and thane, monochlorodifiuoromethane,dichlorotetraflurorothoroughly soluble in common p01y(viny1 chloride)SOL ethylene, trlchloroethylene, chloroform, carbon tetravents chloride,and low boiling hydrocarbons, such as butane,

Now in accordance with this invention it has unex- Pehtahe, hexane,toluene, Accordingly, y pectedly been found that modified foams of vinylchloride 0 POund Whlch decomposes o ti to yield at least polymers can beprepared in a one-step heating process, one mole of gas P mole of'hlowlhg agent at a tempera with or without the application of pressure,by heating a ture f 90 C. or less can be u blend of a vinyl chloridepolymer, a blowing agent and Any hYl ehlOTlde P y p y of 1 3 anazidoformate compound at a temperature sutficient to cohtahhhg at leasttz mole P most f release the gas from said blowing agent, whichtemperaera'hly 60 m P r h chlohlde can he usedhl ture is also effectivefor the modification reaction with pfeparhhoh the 'modlhed foams 1haccordance Wlth the azidoformate compound whereby blowing and modithislhvehhhh Exemplary of these Polymers are P fication of the vinylchloride polymer is effected. By (Y y 0r d V1nylacetate copolymers,using this process, it is possible to produce either rigid or vlhyleh10f1deV1hY1 aeetal P Y Vlhyl ehlendefl ibl foams f any desireddensity, having u if 40 vinylidene chloride copolyrners, vinylchloride-acryloniclosed cell structures. In addition, by regulating theh COPOIYmeTS Vlhyl izy ene drcarboxylrc amount of id f t used, i i 11 1to produce acid alkyl ester copolymers, such as vinyl ChlOIl'dC-dleitherinfusable, insoluble or thermoplastic soluble foams. ethyl fumaratecopolymer-s, vmyl h10r1ded1ethy1 maleate The azidoformates used inaccordance with this incopolymefs; Vinyl eh10Tide VihYhdehe h Y ventionare solids or oils having a boiling point of at trile terpolymers, vinylchloride-vinyl acetate-maleic anleast about 100 C. at a pressure of 70mm. mercury hydride p y e Either P1215550I Plastic grade and h i hgeneral f l vinyl chloride polymers can be used since this invention 0is equally applicable to either type. In addition to the R H above,blends of vinyl chloride polymers with certain OCNK X other polymers canbe used. Exemplarypolymers which where x is at least 1, preferably fromabout 1 to about can be blended with a vinyl chloride polymer are poly-100, and R is an organic radical, inert to modification rechloroprene,'butadiene-acrylonitrile c-opolymers, butaactions, containing at leastone carbon atom per azidodienemethyl isopro-penyl ketone copolymers,butadieneformate group. Exemplary of the azidoformates used vinylpyridine copolyme-rs, butadiene-ethyl acrylate coare the alkylazidoformates such as n-octadecyl azidopolymers, polyisobutylene,polyethylene, styrenebutadiformate, tetramethylene-bis(azidoformate),penthamethene copolyrners, natural rubber, etc. These blends willylene-bis(azidoformate); the cyclic alkyl azidoformates preferablycontain at least about 80% by weight of vinyl such as1,4-cyclohexanedimethyl-bis(-azidoformate), 2- hlo id polymer.(l-p-menthenyl-8-oxy)ethyl azidoformate; 2-norborn-5- Various yp offoams he P p from the Vinyl enyl methylene azidoformate; the aralkylazidoforates Chloride P y described above, depending upon the such asa,ap-xylene-bis(azidoformate); the aromatic Specific P y usedeXamPIe, PY( y azidoformates such as phenyl azidoformate, 2,2-isoproyields rigidand Semi-rigid foams- FleXihle foams are pylidene-bis(p,p'-phenylazidoformate); the azidoformate teihed from P Y( Y chloride) Plastisolsand the Vinyl ethers such as 2,2'-oxydiethyl-bis(azidoformate), 2,2'-Chloride p yoxydipropyl-bis(azidoformate), 2,2-ethylenedioxydiethyl- IIIP p g foams in accordance With s invention, bis(azidoformate), thetetraazidoformate of pentaeryththe Vinyl chloride Polymer is firstblended h n HZidO" ritol-propylene oxide adduct having the generalforformate and blowing agehty desired means can mula be used to bringabout this blending. When a solvent CH3 0 blowing agent is used, aconvenient method for forming 0( 4} 7 the desired expandable blend is tomix the vinyl chloride CH:O-OH3 HOCN3 4 polymer and an azidoformate,pass the mixture through an extruder, chop the extruded material int-opellets and then soak the pellets in the solvent blowing agent until thedesired amount of the latter has been absorbed. When a chemical blowingagent is used, the azidoformate and blowing agent can be mixed with adiluent (which can also contain a stabilizer or other modifier for thevinyl chloride polymer), and then the polymer in finely divided form canbe added and mixed into a slurry. On evaporation of the diluent anintimate mixture of the polymer, blowing agent and azidoformate isobtained. When a poly(vinyl chloride) plastisol is used, theazidoformate and blowing agent can readily be mixed into the dispersion.

The modifying and blowing of the above described expandable blends isthen carried out by heating the blend to a temperature from about 120 C.to about 200 C. The period of time required to effect the desired degreeof blowing will depend on the temperature used etc., but will usually beabout 3 minutes to about 3 hours, more preferably from about 5 minutesto about 1 hour. The exact temperature to be used will then depend onthe azidformate and blowing agent used, the length of time the blend isheated, etc. The modification and blowing usually take placesimultaneously but may take place sequentially, depending on the type offoaming process used. Where blowing is conducted in an open vessel,cross-linking will usually be required to prevent the foam fromcollapsing but must not be complete before expansion. Best results canbe obtained by selecting an azidoformate and blowing agent whichdecompose-s (or volatilize in the case of the solvent blower) at aboutthe same temperature.

The amount of azidoformate used in the preparation of the foams willpreferably be from about 0.1% to about 20%, more preferably from about1% to about by .weight of the polymer. The amount of blowing agentincorporated will obviously depend upon the degree of blowing desired,that is, the density desired for the final foamed product and the typeof blowing agent used. In general, the amount will be within the rangeof from about 1% to about 30% by weight of the polymer.

The following examples are presented for purposes of illustration, partsand percentages being by weight unless otherwise specified. The extentof cross-linking in the examples is indicated by the resultingvulcanizates insolubility in (expressed as percent gel) a solvent, whichis a complete solvent for the uncross-linked polymers. .Percent gel isindicative of the percentage of polymer that is cross-linked.

In the examples, percent gel Was determined as follows: A one-half inchdiameter by 0.050 inch thick discshaped specimen was weighed andmacerated in an excess of the solvent for 4 hours at 80 C. The specimenwas then dried in vacuum for 4 hours at 80 C. and reweighed. The initialand dry Weights were each corrected (for non-polymer components of thespecimen) to a 100% polymer base. From these figures, percent gel iscalculated by the formula corrected dry Weight corrected initial weightExample 1 X l00=percent gel This example illustrates the preparation ofa flexible foam from a poly(vinyl chloride) plastisol, a blowing"P0ly(vinyl chloride) having a specific gravity of 1.40 at 25 C. and aspecific viscosity of 0.60 as determined at 20 C. on a 1% solution inmethyl isobutyl ketone.

Prepared from adipic acid and ethylene glycol.

The formulation was poured into an open beaker and heated for 30 minutesat a temperaure of C. The resulting foam was a uniform, substantiallyclosed cell material having a density of 18 pounds per cubic foot. Itwas tested and found to have a percent gel of 116 as determined incyclohexanone. A control formation was prepared exactly the same wayexcept for the omission of the azidoformate. When the control was heatedat a temperature of 150 C. for 30 minutes, it first expanded and thencompletely collapsed. The resulting material was quite dense and had apercent gel of 0 as determined in cyclohexanone.

Examples 2 and 3 These examples illustrate the preparation of flexiblefoams from the poly(v-inyl chloride) plastisol as described in Example1, using a different blowing agent and a different azidoformate. Eachformulation was poured into an open beaker and heated as described inExample 1. The specific formulations and the density and percent gel (asdetermined in cyclohexanone) of the resulting foams are tabulated below.

e As described in Example 1. b As described in Example 1.

Example 4 This example illustrates the praparation of a semirigid foam.The finely divided sample of the poly(vinyl chloride) described inExample 1, butylbenzylphthalate, dibasic lead phthalate, azobis(formamide), and tetramethylene bis(azidoformate) were slurried in aliquid dispersng blend of 70% n-heptane, 20% toluene, and 10% methylethyl ketone. The liquid dispersant was allowed to evaporate to roomtemperature leaving a dry, white powder containing the following amountsof ingredients.

Ingredients: Parts Poly(vinyl chloride) 100 Butylbenzylphthalate 50Dibasic lead phthalate 0 A20 bis(formamide) '1 Tetramethylenebis(azidoformate) 3 The dry mixture was heated in a closed mold for 5minutes at a temperature of C. and a pressure of 500 psi. The resultingfoam was a semi-rigid, closed cell structure. It was tested and found tohave a percent gel of 89 as determined in methyl ethyl ketone.

Example 5 This example illustrates the preparation of a rigid foam. Theingredients tabulated below were co-dissolved and dispersed in 200 partsof methyl ethyl ketone.

Ingredients: Parts Vinyl chloride-vinyl acetate copolymer 3 100 Dibasiclead phthalate 10 A20 bis (formamide) 1 Tetramethylene bis(azidoformate)3 Containing 85% by weight vinyl chloride and 15% by weight of vinylacetate, having a specific gravity of 1.35 at 25 C. and a specificviscosity of 0.55 as determined at 20 C. on a. 1% solution in methylisobutyl ketone.

The methyl ethyl ketone was allowed to evaporate at room temperature andthe resulting dry mixture heated for 15 minutes at a temperature of 150C. under a pressure of 500 p.s.i. The resulting foam was a rigid, closedcell structure having a density of approximately 18 pounds per cubicfoot. It was tested and found to have a percent gel of 90 as determinedin methyl ethyl ketone.

Example 6 This example illustrates the preparation of a rigid foam of .ablend of poly(vinyl chloride) with chlorinated, low density polyethyleneusing a solvent blowing agent. The following ingredients were compoundedon a two-roll mill at a temperature of 160 C. for 15 minutes.

Ingredients: Parts Poly(vinyl chloride) 90 Chlorinated low densitypolyethylene 10 Mixed barium cadmium laurate 5 Phosphite stabilizer 1Tetramethylene bis(azidoformate) 0.3

a As described in Example 1.

The resulting mixture was chopped into small particles and soaked in 30parts of toluene. The mixture was then placed in a high pressureautoclave and heated in an atmosphere of nitrogen at a temperature of200 C. under a pressure of 600 p.s.i. After 1 hour, the pressure wassuddenly released and the material expanded to the dimensions of theinner wall of the autoclave. The resulting rigid foam consistedpredominantly of closed cells of uniform size and had a density of 4pounds per cubic foot. It was tested and found to have no detectablegel. A control was prepared under the exact same conditions except forthe omission of the azidoformate. After heating in the autoclave andsuddenly releasing the pressure as described above, the control wasremoved and found to consist of a nonuniform, partially expanded shellaround the Wall of the autoclave with a collapsed hollow interior. Whatwe claim and desire to protect by Letters Patent 1. A process forpreparing a modified cellular vinyl chloride polymer material whichcomprises heating a blend of a vinyl chloride polymer with a blowingagent and an azidoformate having a boiling point of at least about 100C. at a pressure of mm. of mercury and having the general formula wherex is at least 1 and R is an organic radical inert to modificationreactions, at a temperature sufficient to release gas from said blowingagent, whereby blowing and modification of the polymer are effected.

2. The process of claim 1 wherein the azidoformate is tetramethylenebis(azidoformate).

3. The process of claim 1 wherein the vinyl chloride polymer ispoly(vinyl chloride).

4. The process of claim 1 wherein the vinyl chloride polymer is vinylchloride-vinyl acetate copolymer.

5. The process of claim 1 wherein the vinyl chloride polymer is a blendof poly(vinyl chloride) and chlorinated polyethylene.

6. An expandable vinyl chloride polymer composition comprising a blendof (l) a vinyl chloride polymer,

(2) a blowing agent, and

(3) an azidoformate having a boiling point of at least about C. at apressure of 70 mm. of mercury and having the general formula where x isat least 1 and R is an organic radical inert to modification reactions.

7. Th composition of claim 6 wherein the vinyl chloride polymer ispoly(vinyl chloride).

8. {like composition of claim 6 wherein the vinyl chloride polymer isvinyl chloride-vinyl acetate copolymer.

9. The composition of claim 6 wherein the vinyl chloride polymer is ablend of poly(vinyl chloride) and chlorinated polyethylene.

10. A vinyl chloride polymer foam prepared by heating the composition ofclaim 6.

No references cited.

MURRAY TILLMAN, Primary Examiner.

1. A PROCESS FOR PREPARING A MODIFIED CELLULAR VINYL CHLORIDE POLYMERMATERIAL WHICH COMPRISES HEATING A BLEND OF A VINYL CHLORIDE POLYMERWITH A BLOWING AGENT AND AN AZIDOFORMATE HAVING A BOILING POINT OF ATLEAST ABOUT 100*C. AT A PRESSURE OF 70 MM. OF MERCURY AND HAVING THEGENERAL FORMULA